Extensible coupling for well pipes

ABSTRACT

An extensible coupling for use in well pipe strings, particularly, rotary drill strings, to permit relative longitudinal, non-rotative movement between sections of the pipe string. The coupling comprises an outer tubular member adapted to telescopically receive an inner tubular member. The inner tubular member is provided with a plurality of longitudinal spline slots engaged by rollers carried by the outer tubular member and projecting radially inward from its bore.

United States Patent [191 Brown [451 Apr. 10, 1973 EXTENSIBLE COUPLING FOR WELL PIPES Inventor:

[76] Cicero C. Brown, 8490 Katy Freeway, Houston, Tex. 77024 Filed: Aug. 5, 1971 Appl. No.: 169,319

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 50,794, June 29,

1970, Pat. No. 3,630,551.

U.S. Cl. ..285/9l, 287/53 SS, 285/330 Int. Cl. ..Fl6c 25/00 Field of Search ..285/9l, 330, 302;

[56] References Cited UNITED STATES PATENTS 3,319,726 5/1967 Brown ..l6 6/.5 X 3,406,537 10/ 1968 Falkner ..64/23 Primary Examiner-Andrew V. Kundrat Attorney-Carlos A. Torres et al.

[ ABSTRACT 10 Claims, 3 Drawing Figures EXTENSIBLE COUPLING FOR WELL PIPES CROSS-REFERENCE TO OTHER APPLICATION This application is a continuation-in-part of the copending application of Cicero C. Brown, Ser. No. 50,794 filed June 29, 1970 and now U.S. Pat. No. 3,630,551.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention pertains to pipe couplings. In particular, it concerns couplings which permit relative longitudinal movement between sections of pipe connected by the coupling while preventing relative rotation of the sections.

2. Description of the Prior Art In drilling wells by the conventional rotary method, particularly from a floating drilling platform, the platform will be subjected to vertical movements in response to the passage of waves over the surface of the water body in which it is afloat. This necessarily produces a corresponding up and down movement of the drill pipe string, which is a serious hindrance to the drilling operation, particularly to maintenance of a constant weight on the drill bit during the drilling operation, since upward movement tends to pull the bit and drill collars off bottom while'downward movement may tend to apply undue downward pressure on the drill string and the bit.

Various types of extensible couplings, commonly called slack joints or drill splines, have heretofore been employed to overcome this difficulty by providing an extensible coupling in the drill pipe string which will allow for the vertical movements of the floating platform while maintaining the bit in constant contact with the bottom of the well and at the same time maintaining rotation of the drill string necessary to turn the drill bit. Such conventional joints employ various forms of spline connections between telescoping members of the coupling to accommodate thev longitudinal movement which occurs. However, such conventional couplings are subject to very severe wear and to unbalanced pressure forces such that they must be replaced frequently and may, in some instances,

bearings arranged therebetween to provide relatively friction free movement between the coupling members. A highly effective sealing unit was also provided between the members.

In this earlier form of coupling, the male splines were welded in place in the outer coupling member after the bearings were in place between the spline members. The male spline thus became an integral partof the outer coupling member. This construction has been found to have certain disadvantages, primarily because of limitation on the ability to replace the bearings readily when they became worn. It was also found, particularly where the bearings were ball bearings, that due to the torsional stresses to which the coupling was exposed, the wearing in the bearing races was uneven, a greater degree of wear occurring at one end than at the other. The nature of this wear was such, however, that it was found, after a period of use, that if the male spline could be turned end-for-end relative to the female splines, the races in the coupling would be restored substantially to their original form and efficiency, thereby greatly extending the useful life of the coupling. Due, however, to the welded construction theretofore employed, it was found to be generally impractical to effect the desired reversal of the male splines without greatly weakening or even destroying the coupling.

Furthermore, in the earlier form of the coupling, the spline members and bearings associated therewith were lubricated only by the well fluid and contact therewith. Such fluids are-sometimes poor lubricants and may contain abrasive materials which result in undue wear on the spline members.

An improved form of the coupling is disclosed in the aforementioned patent application Ser. No. 50,794

which reduces the disadvantages of the earlier form. In

. the improved version, the male splines are removably become broken by-reason of the extensive wear thereon. Moreover, many of the conventional couplings are made relatively complex in an effort to meet the conditions encountered and their complicated construction necessarily creates problems in maintaining the parts in efficient working condition under the severe loads frequently imposed thereon.

Furthermore, under the severe operating conditions commonly encountered, conventional couplings are subject to leakage between the coupling members. This may permit circulating drilling fluid to bypass the drill bit, with a consequent loss of drilling efficiency.

A form of coupling designed to successfully meet the aforedescribed conditions has heretofore been disclosed and patented by the present applicant and James D. Mott in U. S. Pat. No. 3,504,936, issued April 7, 1970. The coupling therein disclosedcontemplated a structure employing tubular telescoping members connected for longitudinal relative non-rotative movement by a spline connection comprising elongate male splines on the outer member received in female spline grooves on the inner member and having anti-friction mountable in suitable openings in the outer coupling member so that they can be removed at will, turned end-for-end and reinstalled to restore the coupling substantially to itsoriginal efficiency and extend the life of the coupling. In addition, seals are provided for sealing the spline members within a chamber which may be filled with a suitable lubricant.

Although the improved version offers substantial advantages over the earlier form, it also has some disadvantages. The mounting of the male spline members is accomplished by a plurality of screws which under the severe forces applied thereto, frequently work out of engagement with their threaded holes, occasionally resulting in damage to the coupling. A considerable amount of time is also required to turn the male splines end-for-end or to replace them. Furthermore, with the seal chamber of the improved version, the length of the coupling must be increased to provide engaging surfaces for the seals.

SUMMARY OF THE INVENTION The present invention contemplates still a further improvement in a spline type extensible coupling which eliminates most of the disadvantages of the prior forms. As in the earlier form, the coupling of the present invention comprises tubular telescoping members connected for longitudinal relative non-relative movement by a spline connection. The spline connection comprises female longitudinal spline grooves on the inner member and radially inward projecting roller members carried by the outer member. The roller members function as male splinestand engage the female spline grooves for longitudinal movement therein. These rollers are attached to the outer member by dovetailed key strips, allowing them to be easily replaced and preventing failure of the male spline mounting. The roller design also results in more even wear.

In addition, the coupling of the present invention is provided with an improved seal assembly for immersing the spline connection in a lubricant filled chamber. This seal permits the coupling member to be several feet shorter than the sealed chamber design of one of the prior forms.

Still other objects and advantages of the invention will become more readily apparent from the accompanying drawings and detailed description which follows hereafter.

BRIEF DESCRIPTION OF THE DRAWINGS I coupling of FIG. 1 taken along line 22 thereof; and

FIG. 3 is a cross-sectional view of the exemplary coupling of FIG. 1 taken along line 3-3 thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the coupling comprises a tubular male member, designated generally by the numeral 10, anda tubular female member designated generally by the numeral .11, adapted to telescopically receive the male member for limited relative longitudinal movement therein. The male member 10 comprises an upper tubular section 15 and a lower tubular section 16 connected by a pin and box connection 17. The upper section 15 is provided with a threaded box 18 for connection to'the pipe string 20.

The outer female member 11 is also made up of a plurality of coaxial interconnected sections, comprising an upper spline carrying section 21, intermediate section 22 and lower seal carrying section 23. A threaded pin and box connection 25 connects upper section 21 to intermediate section 22 and another threaded pin and box connection 27 connects intermediate section 22 to lower section 23. The lower section 23 is provided with a pin member 28 for connection with-a subadjacent section of the pipe string 20. Connected to the upper end of the upper section 21 by a threaded pin and box connection is a retainer collar 32, the purpose of which will be more clearly understood hereafter.

The upper section 15 of male member 10 is provided with a plurality of longitudinal spline slots 35 which form the female portion of a spline connection between inner member 10 and outer member 11. In cross-seetion, the side walls 36 of the slots 35 lie substantially along radial lines projecting from the axis of the inner member 15 so as to flare outwardly from the bottom wall 37. The male component of this spline connection comprises a plurality of roller assemblies 40 mounted in holes provided therefor in upper section 21' of female member 11. These roller assemblies comprise a cylindrical mounting element 42 and a tapered roller 44. Seals 48 are provided around the mounting element 42. The rollers 44 are mounted for rotation on a shaft portion .45 extending from mounting element 42. The rollers 44 are thus mounted for radial projection into the spline slots 35. The tapered rollers 44 engage the side walls 36 of the slots 35 allowing the male member 10 and female member 11 to be non-rotatingly longitudinally displaced relative to each other while the roller elements 44 roll along their respective slots 35. The tapered rollers 44 engage the side walls 36 of the slots 35 allowing the male member 10 and female member 11 to be non-rotatingly longitudinally displaced relative to each other while the roller elements 44 roll along their respective slots 35 The roller assemblies 40 are attached to upper section 21 in a unique fashion. The outer end of the mounting elements 42 are provided with transverse dovetail key slots 51. The upper section-21 of female member 11 is also provided with corresponding longitudinally disposed dovetail key slots. On assembly, the key slots 51 of the roller mounting elements 42 are longitudinally aligned with the key slots in upper section 21. Dovetail key strips 61 are then longitudinally fed into the slots 51 until they assume the fully engaged position shown in FIG. 1. The retaining collar 32 prevents the keys 61 from coming out. Thus, the roller assemblies 40 are rigidly attached to the female member upper section 21. To remove the roller elements 44 for repair or replacement, the retaining collar 32 must be removed and the key strips 61 must be displaced. Each of the mounting elements 42 is provided with a tapped hole 62 for engagement by a pulling tool.

Another unique feature of the invention is the sealing apparatus associated with the splined connection. Annular seal assemblies and above and below the roller assemblies 40 are carried by the upper section 21 of female member 11. Each of these seal assemblies 70, 80 comprises resilient seal elements 72, 82, which slidingly and sealingly engage the walls of the spline slots 35 and other external surfaces of section 15 of the male member 10. Seals 73 and 83 engage the interior of section 21. The lower seal assembly 80 is stationarily tion in the spline connection for a longer life of the tool. Although this construction is much less likely to leak than the prior forms, the limited permissable movement of seal assembly 70 allows well fluids to force seal assembly 70 to take up any slack due to lubricant leakage. Since the seal assemblies 70 and 80 engage the spline area of section 15, it is not necessary, as in previous forms, to provide additional seal engaging surfaces which increase the overall length of the coupling.

Another seal assembly, designated generally by the numeral 100, provides a sliding seal between male member 10 and female member 11. Such a seal assembly is fully described in the aforementioned U. S. Pat. No. 3,504,936 and will not be described in detail herein, except to note that it is held on the lower section 23 by annular shoulder 101 and retainer ring 102. Its purpose is, of course, to prevent loss of fluid from the pipe string or contamination by the fluid surrounding the coupling.

It is evident that in operation the coupling members 10 and 11 may be relatively extended and retracted, depending on the relative movements of the pipe string 20 above and below the coupling. The spline connection including the spline slots and roller assemblies permit relatively frictionless, longitudinal movement under the various stresses to which pipe string 20 may be subjected while preventing relative rotation. The seal assemblies 70 and 80 constantly immerse the spline connection in lubricant while the lower seal assembly 100 prevents leakage of fluid into and from the pipe string. The extension of the coupling may be limited by the engagement of the stop ring 105 on male member 10 with retainer ring 86 on female member 11. Retraction may be limited by the engagement of upper section shoulder 107 with retainer collar 32. During the extension and retraction of the coupling, well fluids will enter into and be displaced from annular spaces between male member 10 and female member 11 through ports 109 in the walls of intermediate section 22 It is readily apparent that the spline connection of the present invention is much preferred over the prior forms. Friction is reduced to a minimum. Provision is made for easy replacement of the male spline elements, roller assemblies 40. Furthermore, a much improved seal arrangement is provided which reduces the overall length of the coupling and reduces the possibilities of leakage from the lubricant chamber in which the male spline elements are immersed.

Although only one embodiment of the invention has been described herein, many changes and modifications may be made by those skilled in the art without departing from the spirit of this invention. It is therefore intended that the scope of the invention be limited only by the claims which follow.

lclaim:

1. An extensible coupling for well pipe strings, comprising:

a. telescopically engaged inner and outer tubular members;

b. means carried by each of said members for connecting them to adjacent sections of a pipe string; and

0. male and female spline elements cooperably disposed respectively on said outer and inner members to form a non-rotating longitudinally slidable connection between said members, said male spline elements comprising a plurality of roller assemblies detachably mounted in holes provided in said outer member for radially inward projection into engagement with said female spline elements;

d. said female spline elements comprising longitudinal slot means, said roller assemblies comprising roller, means mounted on mounting means for rotation about axes substantially perpendicular to I .the longitudinal axis of said members and engaging said slot means for travel therein;

e. said mounting means being held in said holes by key means comprising a dovetail key member longitudinally disposed relative to said tubular members and longitudinally engagable with longitudinally alignable dovetail slots in said mounting means and said outer member.

2. An extensible coupling as set forth in claim 1 including a sealing assembly positioned in sealing relation between said coupling members below said slidable connection.

3. An extensible coupling as set forth in claim 2 including second and third sealing assemblies carried by said outer tubular member above and below said roller assemblies, respectively, for sliding and sealing engagement with said female spline elements to form a reciprocating chamber in which said roller means may be continuously immersed in a lubricant in said chamber.

4. An extensible coupling as set forth in claim 1 in which said key member is releasably maintained in engagement with said dovetail slots by releasable retainer means.

5. An extensible coupling for well pipe strings, comprising:

a. telescopically engaged inner and outer tubular members; I b. means carried by each of said members for connecting them to adjacent sections of pipe string;

0. male and female spline elements cooperably disposed respectively on said outer and inner members to form a non-rotating, longitudinally slidable connection between said members; and

d. seal means carried by said outer member above and below said male spline elements slidingly and sealingly engaging said female spline elements to form a movable chamber in which said male spline elements may be continuously immersed in a lubricant in said chamber.

6. An extensible coupling as set forth in claim 6 including a sealing assembly positioned in sealingrelation between said coupling members below said slidable connection.

7. An extensible coupling as set forth in claim 5 in which said female spline elements comprise a plurality of longitudinal slot means and in which said male spline elements comprise a plurality of roller means projecting radially inward from said outer means for rotation about axes substantially perpendicular to the longitudinal axis of said members.

8. An extensible coupling as set forth in claim 7 in which said roller means are detachably mounted in holes through the wall of said outer member.

9. An extensible coupling as set forth in claim 8 in which the sides of said slot means are radially disposed with respect to the axes of said members, said roller means comprising rollers tapered to mutually engage said slot means sides for rolling contact therewith.

10. An extensible coupling as set forth in claim 5 in which said seal means comprising a first sealing assembly above said roller assemblies and a second sealing assembly below said roller assemblies, one of said sealing assemblies being mounted on said outer member for limited axial movement relative thereto to compensate for loss of lubricant from said movable chamber. 

1. An extensible coupling for well pipe strings, comprising: a. telescopically engaged inner and outer tubular members; b. means carried by each of said members for connecting them to adjacent sections of a pipe string; and c. male and female spline elements cooperably disposed respectively on said outer and inner members to form a nonrotating longitudinally slidable connection between said members, said male spline elements comprising a plurality of roller assemblies detachably mounted in holes provided in said outer member for radially inward projection into engagement with said female spline elements; d. said female spline elements comprising longitudinal slot means, said roller assemblies comprising roller means mounted on mounting means for rotation about axes substantially perpendicular to the longitudinal axis of said members and engaging said slot means for travel therein; e. said mounting means being held in said holes by key means comprising a dovetail key member longitudinally disposed relative to said tubular members and longitudinally engagable with longitudinally alignable dovetail slots in said mounting means and said outer member.
 2. An extensible coupling as set forth in claim 1 including a sealing assembly positioned in sealing relation between said coupling members below said slidable connection.
 3. An extensible coupling as set forth in claim 2 including second and third sealing assemblies carried by said outer tubular member above and below said roller assemblies, respectively, for sliding and sealing engagement with said female spline elements to form a reciprocating chamber in which said roller means may be continuously immersed in a lubricant in said chamber.
 4. An extensible coupling as set forth in claim 1 in which said key member is releasably maintained in engagement with said dovetail slots by releasable retainer means.
 5. An extensible coupling for well pipe strings, comprising: a. telescopically engaged inner and outer tubular members; b. means carried by each of said members for connecting them to adjacent sections of pipe string; c. male and female spline elements cooperably disposed respectively on said outer and inner members to form a non-rotating, longitudinally slidable connection between said members; and d. seal means carried by said outer member above and below said male spline elements slidingly and sealingly engaging said female spline elements to form a movable chamber in which said male spline elements may be continuously immersed in a lubricant in said chamber.
 6. An extensible coupling as set forth in claim 6 including a sealing assembly positioned in sealing relation between said coupling members below said slidable connection.
 7. An extensible coupling as set forth in claim 5 in which said female spline elements comprise a plurality of longitudinal slot means and in which said male spline elements comprise a plurality of roller means projecting radially inward from said outer means for rotation about axes substantially perpendicular to the longitudinal axis of said members.
 8. An extensible coupling as set forth in claim 7 in which said roller means are detachably mounted in holes through the wall of said outer member.
 9. An extensible coupling as set forth in claim 8 in which the sides of said slot means are radially disposed with respect to the axes of said members, said roller means comprising rollers tapered to mutually engage said slot means sides for rolling contact therewith.
 10. An extensible coupling as set forth in claim 5 in which said seal means comprising a first sealing assembly above said roller assemblies and a second sealing assEmbly below said roller assemblies, one of said sealing assemblies being mounted on said outer member for limited axial movement relative thereto to compensate for loss of lubricant from said movable chamber. 